Question:
Seeta Devi has Rs 9 in fifty-paise and twenty five-paise coins. She has twice as many twenty-five paise coins as she has fifty-paise coins. How many coins of each kind does she have?
Solution:
Let the number of 50 paise coins be $\mathrm{x}$.
Therefore, the number of 25 paise coins will be $2 \mathrm{x}$.
Value of 50 paise coins $=$ Rs. $0.5 \mathrm{x}$
Value of 25 paise coins $=$ Rs. $0.25 \times 2 \mathrm{x}$
According to the question,
$0.5 \mathrm{x}+0.25 \times 2 \mathrm{x}=9$
or $\mathrm{x}=9$
$\therefore$ Number of fifty paise coins $=9$
Number of twenty five paise coins $=2 \times 9=18$
Total number of coins $=9+18=27$.